This invention relates to image processing methods and apparatus, and more particularly to methods and apparatus for producing an output image in which certain features in an input image stand out or are more readily differentiated from the remainder of the input image.
As is discussed, for example, in commonly assigned, Casasent U.S. Pat. No. 4,906,099 (which is hereby incorporated by reference herein), optical image processing offers many advantages in such applications as high-speed optical product inspection. The methods and apparatus employed in the above-mentioned Casasent patent application process a two-dimensional input image, for example, by focusing all of the input image information down to a line or one-dimensional output image. This causes any bright line in the input image which is perpendicular to the longitudinal axis of the output image to appear as a very bright spot in the output image. The presence or absence, location, and/or intensity of this bright spot in the output image can be used to detect such properties of the input image bright line as its presence or absence, proper alignment perpendicular to the output image axis, location, brightness, etc.
Quite often in using techniques of the type described above, it will be desired to test a line which is no brighter than an adjacent area, or a line which is less bright than an adjacent area. For example, it may be desired to locate the edges of a surface of a rectangular product. Such edges often tend to reflect light less strongly than the remainder of the surface because the exterior of the product is bent or folded at the edges. As another example, it may be desired to test the edges of some of the bolder lettering or other ornamentation on the surface of the product, but such edges are very often defined by transitions from bright to dark portions of the image rather than by bright lines.
From the foregoing it will be apparent that it would be desirable to be able to enhance certain features of an input image to facilitate subsequent inspection or other processing of the image with respect to those features.
It is therefore an object of this invention to provide methods and apparatus for optically enhancing selected features of an input image.
It is a more particular object of this invention to provide methods and apparatus for filtering an input image so that portions of the image having a particular light level (which may be, for example, an intermediate light level) are passed (or alternatively attenuated) by the apparatus, while other portions having other light levels are attenuated (or alternatively passed) by the apparatus.